This invention relates to the filtration field, and more particularly, to an improved low hold up biological fluid filtration system, including a low hold up biological fluid filter device capable of filtering biological fluids, including the removal of components or chemicals from blood or blood products, and including the removal of leukocytes from packed red cells, and prions from blood or blood products.
There are currently available filtration devices for filtering blood or blood products. The currently available devices use multiple layers of filtration media of different pore size, but of the same diameter. Some devices use a vent filter to drain the upstream side of the filtration device after filtration is complete to minimize hold up volume. These vent filters either have to be isolated from the fluid being filtered during the filtration cycle by a clamp or valve which has to be manually opened once filtration is complete to drain the device, or in an automatic system multiple layers of different pore size vent filter media must be used to prevent fouling the vent filter during the filtration cycle. Some of these devices require a negative pressure on the outlet of the device to eliminate air from the downstream side of the device. In all of the devices a quantity of biological fluid will flow from the outlet of the device before all of the air has been purged from the device. For a device to be usable in bed side applications (i.e. for direct transfusion to a patient), the amount of biological fluid that flows from the outlet of the device before all of the air has been purged from the device must be minimized. Furthermore, currently available filtration devices are designed to filter one type of blood or blood product per device.
It is therefore an object of the present invention to provide a biological fluid filtration system including a biological fluid filtration device that runs automatically, minimizes hold up volume, does not require a negative pressure at the outlet to eliminate air from the down stream side of the biological fluid filtration device, and in several embodiments use smaller surface area downstream filter elements to reduce hold up volume of the device. It is also an object of the present invention to minimize the amount of biological fluid that flows from the outlet of the biological fluid filtration device before all of the air has been purged from the device, so that the biological fluid filtration device will be usable in bed side applications. It is a further object of the present invention to eliminate the need for vent filters to drain the upstream chamber of the biological fluid filtration device after the filtration cycle has been completed. Another object of the present invention is to be able to filter two different types of blood or blood product using a single biological fluid filtration device that includes two independent fluid flow paths, without fluid flow communication between the two fluid flow paths. For example leukocytes could be removed from packed red cells through one fluid flow path, and leukocytes could be removed from a platelet concentrate through the other fluid flow path. It is also an object of the present invention to provide a single vent filtration device that can vent the two fluid flow paths of a biological fluid filtration device that includes two independent fluid flow paths.